The present invention relates to a viewing device for installation on a door, and more particularly to such a device which permits at various times viewing straight ahead, laterally to both sides, and downwardly.
The problem of home security is well documented. Throughout history, the greatest problem has been simply to identify a caller seeking admission to a house or other dwelling. People have employed many devices to augment their ability to identify a caller. For centuries peepholes of one sort or another have assisted in identifying potential entrants. The traditional peephole has been refined over the years to include the use of ultra-wide angle "fish-eye" lenses to enhance the field of view and camouflage, like one-way glass, to conceal the observer within.
Generally multi-family dwellings and in particular the urban apartment house present special problems. For example, ambient hallway lighting may be inadequate, and irregularly-shaped hallways make ideal hiding places for persons seeking to avoid detection.
There have been several attempts at evolving a device to obtain a wider and clearer viewing field. However, devices in accordance with the prior art have a multiplicity of problems, including one or more of the following: reduced viewing acuity, a pronounced lack of reliability, liability to tampering, and encouraging the spread of fire.
U.S. Pat. No. 3,973,835 issued to Miyakawa et al. discloses a periscope device which includes a fixed one-way or see-through mirror. The viewer looks through the one-way mirror to achieve an axial view, and by appropriately positioning the mirror accomplishes radial viewing. However, the mirror acts as a filter and decreases the amount of available light reaching the eyepiece during axial viewing.
U.S. Pat. No. 4,050,792 discloses a viewing device which is comprised of a housing and three separate viewing elements which afford a panoramic view. The field of view is inherently limited by the placement of the individual viewing elements, making right-angle viewing unobtainable. Moreover, the separate viewing elements require the viewer to align his line of sight through three separate apertures. Finally, the construction of the device would encourage the spread of fire as the mounting hole, cut through the door, could act as a sizable chimney drawing flames therethrough.
U.S. Pat. No. 4,964,711 issued to Degnan discloses a viewing device which includes a swingingly fixed mirror having an opaque reflecting surface which aligns with a plurality of surveillance ports. By turning the eyepiece, the viewer swings the mirror into position in front of the surveillance port to be accessed to achieve radial viewing, and by further turning of the eyepiece withdraws the mirror from an axial line of sight so that axial viewing is achieved. However, because the effecting of a line of sight between the view port on one side of the door and a surveillance port on the other side of the door, whether directly or via the mirror, is not made manifest to the viewer (except visually), the viewer is frequently confused and cannot determine when the intended line of sight has been achieved where the visual indication is not readily perceptible (for example, where the hall lighting is very dim). While there may be an indication on the eyepiece to enable the viewer to determine when a line of sight has been achieved (and even which line of sight has been achieved), such a visual indication on the eyepiece is, of course, of no use to the viewer who has his eye pressed against the viewing port within the eyepiece and hence cannot see the markings on the eyepiece.
Accordingly, it is an object of the present invention to provide a viewing device affording a high level of viewing acuity along all pertinent lines of sight.
Another object is to provide such a viewing device wherein all pertinent lines of sight afford generally equal viewing acuity.
A further object is to provide such a device which acts as a fire barrier.
It is also an object of the present invention to provide in a preferred embodiment such a device which communicates in a non-visual manner with the viewer, to indicate when one of the possible lines of sight has been achieved.
It is another object to provide such a device which is characterized by a high level of reliability and a high resistance to tampering.
It is a further object to provide such a device which is simple and easy to manufacture, use and maintain.